This revised application is the second competitive renewal of the investigators' Program in Interdisciplinary Training in Environmental Health Sciences (EHS) at Columbia University. Since its inception in 1997, the EHS doctoral program has trained 26 Ph.D. pre-doctoral candidates, 13 of whom have been supported by this training grant. This interdisciplinary program combines public health with basic biomedical science skills and trains students to solve complex problems in three areas of environmental health: cancer, respiratory disease, and neurological disease, within two tracks: Molecular Toxicology and Molecular Epidemiology. The investigators' primary goal is to develop the next generation of independent, academic researchers in environmental health sciences. The Ph.D. program has thrived in a rich, collaborative and collegiate atmosphere that supplements classroom instruction and research with training in writing, public speaking, and teaching. The training faculty consists of 21 well-funded investigators, who collectively have substantial experience in mentoring both pre-doctoral and postdoctoral trainees. These investigators conduct research related to one or more of the Program's focus areas and are highly experienced in its collaborative, interdisciplinary aspects. The training program benefits greatly from its integration with numerous other environmental health activities within the Department, the School, and across the University. These include: the Center for Environmental Health in Northern Manhattan (CEHNM), the Columbia Center for Children's Environmental Health (CCCEH), the Superfund Research Program (CU-SRP) and the Columbia Earth Institute. This training grant, along with Departmental and University support, provides the core funding used to recruit Ph.D. candidates into the Program. By the end of their second year, trainees are typically supported on his/her mentor's R01 grant or on an individual fellowship. This frees up training slots to enable the recruitment of new candidates. Of the nine current students (which includes two underrepresented minorities), six are either currently supported or have been supported by the training grant. Presently, this training grant supports three doctoral candidates but because of the growth of the Department's program faculty, the renovation of its infrastructure, and the increasing number of high quality applicants, the investigators feel that the time is right to extend training grant support to an additional student. Therefore, this application is requesting support for four students so that the doctoral program can grow along with other aspects of the Department. The success of this program is exemplified by the outstanding success of the graduates in finding excellent post-doctoral positions; earlier graduates now hold faculty positions, while several are in senior positions in both industry and related governmental agencies. The renewal of this training grant will assure the continued success of this Program.